I. Field of the Invention
The disclosed embodiments relate to the field of communications, and more particularly, to communications in accordance with the code division multiple access (CDMA) technique.
II. Background
A system for wireless communications in accordance with the CDMA technique has been disclosed and described in various standards published by the Telecommunication Industry Association (TIA). Such standards are commonly known as TIA/EIA/IS-2000 and TIA/EIA/95A\B, among several others, and titled as Mobile Station-Base Station Compatibility Standard for Wideband Spread Spectrum Cellular Systems, incorporated by reference herein. The standards have been evolving over the past several years. The early version of the CDMA system allows communications between base stations and mobile stations in a fixed length time frame and at multiple data rates. The more recent version of the standard, commonly known as the IS-2000 standard, allows communications via different size time frames and at higher data rates than the earlier version.
To maintain communications between a mobile station and a base station, a forward link, from the base station to the mobile station, and a reverse link, from the mobile station to the base station, may be established. At a receiving end of the reverse link communications, the receiver may receive data frames at different data rates. The receiver may have limited resources for processing the received data frames. A communication resource, known as a channel element, allocated for processing a data frame may include one or more fingers for correlating with different multi-path signals. The channel element demodulates the data symbols in each received data frame. Each assigned finger provides symbol energy in accordance with a timing hypothesis. The received energies of each symbol are summed to output a data symbol. The number of data symbols in a frame of data depends on the data rate of the frame. A frame of data contains more data symbols at high data rates than at low data rates. As such, processing a frame of data takes more resources at high data rates than at low data rates.
At a base station, the data frames received from different mobile stations may be at different data rates. In a system operating in accordance with the IS-2000 standard, a receiver in a base station with limited resources may have to process data symbols at a wide range of data rates for a number of mobile stations in reverse link communications with the base station. Therefore, in accordance with the IS-2000 standard, when data frames at high data rates are received, a limited number of communication resources may be allowed for processing data frames at low data rates.
It is to this end as well as others, that in a receiver with a limited number of resources, there is a need for a method and apparatus for efficient use of the resources.